Dilatation balloon catheters are frequently used for the treatment of stenosis in the coronary arteries. This procedure, known as percutaneous transluminal coronary angioplasty (PCTA), was developed by Dr. Andreas Gruntzig. According to this procedure, blockage in a coronary artery can be reduced by positioning a balloon dilatation catheter across the blockage and inflating the balloon, which causes stretching of the artery and pressing of the lesion into the artery wall to re-establish acceptable blood flow through the artery. The first marketable PCTA catheters for angioplasty were "fixed wire" catheters, in which a core or guidewire was fixed within the catheter to stiffen it so that it could be pushed into position in the vascular system. If a different catheter size was required, the fixed wire catheter had to be completely removed and a new one inserted. This is a tedious and time consuming process.
Dr. John Simpson and Dr. Edward Robert subsequently developed an "over-the-wire" catheter in which a guidewire was slidably placed within a lumen of the catheter. The guidewire lumen passed from the distal end of the catheter through the balloon to the proximal end of the catheter. This system provided reasonably easy placement of the catheter because the guidewire was inherently smaller and more flexible than the fixed wire system so one could more readily select the desired coronary artery and reach smaller branches. Once the guidewire was positioned beyond the stenosis, the catheter was then slid over the guidewire so that placement of the balloon spanned the stenosis and the balloon was then inflated. Once the catheter has been inflated to dilate the stenosis, it is not uncommon for the physician to require use of a subsequent larger size of catheter to open the artery. There are different methods used to exchange the catheter and all of them have the same goal, to exchange the catheter without losing the position across the stenosis.
When performing the catheter exchange it is important to keep the guidewire in the same position so that the guidewire may be used to guide the next catheter to the stenosis. The most common method of exchange is to remove the initial guidewire and replace it with an exchange wire that is over double the length of the catheter. Once the exchange wire is in place, the catheter is slid over the exchange wire and the catheter is removed, then the next catheter is slid over the exchange wire to the stenosis. This procedure is time consuming and awkward.
Another method of exchanging the catheter is to use an extension wire. The extension wire is attached to the proximal end of the guidewire that is already in place. With the extension wire attached, the combination of the guidewire and extension wire is approximately the same length as an exchange wire. The advantage of this method is that the original guidewire that has already crossed the stenosis does not have to be disturbed during the catheter exchange.
There are different methods of attaching the extension wire to the guidewire. U.S. Pat. No. 4,917,103 to Gambale describes a male/female connection between the guidewire and extension wire that crimps the extension wire to the proximal end of the guidewire making a permanent connection. U.S. Pat. No. 5,197,486 to Frassica describes a connection where the proximal end of the guidewire has a reduced diameter male element that attaches to a female element at the distal end of the extension wire by using a interference fit. U.S. Pat. No. Re. 34,366 to Taylor describes another male/female connection between the guidewire and the extension wire.
There are other methods that add intermediate parts between the guidewire and extension wire that connects them together (see U.S. Pat. No. 5,188,621 to Samson, U.S. Pat. No. 5,271,415 to Foerster, U.S. Pat. No. 5,234,002 to Chan, U.S Pat. No. 4,922,923 to Gambale, U.S. Pat. No. 5,031,636 to Gambale) or use retractable sleeves which enclose interlocking members of the guidewire and extension wire (see U.S. Pat. No. 5,109,867 to Twyford).
There are problems associated with the aforementioned connections. Connections that use male/female friction to hold the wires together may disconnect if any torsional forces are used during the exchange. Connections that use crimping devices require special equipment, may be somewhat awkward to use and are not readily disconnectable. Connections with intermediate parts cannot connect the wires if those parts are lost or misplaced during a procedure. Connections using retractable sleeves may jam or stick with foreign material and not allow the connection.
The object of the invention is to provide a new and improved guidewire extension that cures the problems that have been encountered by prior extension systems. This is accomplished by making a connection between the guidewire and the extension wire that makes it simple to attach the wires together, can transfer torsional forces between the wires without the fear of the wires coming apart or unscrewing and can be readily disconnected/reconnected when required.